1. Field of the Invention
The present invention relates to an image-processing technique, and, more particularly, to a method of enhancing an image by optimizing exposure and grayscale and to an adaptive exposure-setting method using the same.
2. Description of the Related Art
When an image-capturing apparatus, such as a digital camera, captures an image, an image area that is not covered by automatic exposure control (AE) may occur in specific environments, such as a backlit environment, a dark environment, and a high-contrast environment.
In order to solve this problem, an image-capturing method using a high dynamic range (HDR) sensor or a method of capturing a plurality of images, and combining the images has been proposed. However, the HDR sensor is difficult to design, and is costly to manufacture. In addition, the method of combining a plurality of images requires a process of determining the exposure time of each image, a process of capturing each image, and a process of combining the captured images, and thus it requires a lot of time to process image signals.
Therefore, in order to correct an image captured by a general image-capturing device to enhance the quality of the image, the following processes are needed: a process of estimating an external luminance level; a process of obtaining a sensor-response model on the basis of the estimated valve; a process of setting the exposure in consideration of post-correction to acquire an image; and a process of appropriately adjusting the luminance and contrast of the acquired image.
That is, an image-correcting technique capable of acquiring a high-resolution image using the existing image-capturing apparatus and signal-processing method is needed. This image-correcting technique can be applied to an image signal processor (ISP) that processes an image captured by an image-capturing device, such as a digital camera, or a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) of a camera phone.